This applet should be useful in picking up
vector addition and subtraction. You draw two vectors of your
choice, choose the operation (Add or Subtract) and arrange
the two vectors in a certain manner by dragging them. Drawing
is done by pressing the mouse button at some point and
dragging and releasing it at another point. If you watch the
display you would see it updating giving the details of the
vector that you are drawing. Once you have two vectors on the
drawing space any one of them can be moved. Press the mouse
button with cursor positioned on the dot at the midpoint of
the vector and drag it. This will help you to reposition the
vector parallel to itself

The vectors can be modified after drawing
both by using the cursor keys on the keyboard. Using the
cursor keys with contol key pressed will amplify the effect.
The selection label in the bottom panel will indicate the
color of the vector that will be trimmed. By pressing on the
dot at the midpoint of any vector the selection can be
changed.

Now for the manipulation:

To add, the vectors have to be arranged in
order, that is with tail of one touching the tip of another.
The sum vector is drawn by the applet if the you arrange the
vectors so.

To subtract the vectors have to be arranged
in improper order, that is, tips or tails of the two vectors
should be made to touch. Again the applet draws the
difference vector when the vectors are properly arranged.

Let me explain the subtraction part a bit.
When you have A and B in improper order the vector joining
the free ends is A - B or B - A depending on the direction. This
vector is A - B, if it is in order with B and B - A, if it is in order with A. In the applet the vector A - B is
being drawn. So this would be in order with B.

So draw away merrily and get a feel for the
addition and subtraction of vectors.

Remember

To add - the vectors should be in order (tail
of one touching the tip of another) and

To subtract - the vectors should be in
improper order ( tails of the two vectors or tips of the two
vectors should be touching each other)